D5DBY
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Jet-engine, Flame Out?

Fri Sep 02, 2005 5:52 am

hi

im wondering about if a jet-engine( on a regular jet like MD80, B757) could "stall" and flame out?

ive heard about this...but would an engine flame out if u are flying to slowly..??

like if u are flying at cruise speed and then beginning to stall the AC....would the engine suffer a flame out?

and why is this....beacuse the compressor in the jet-engine dosent get enough air??
 
lowrider
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 6:05 am

possibly. Check out the Pinnicle crash from late last year. If the airflow is sufficiently disruupted, it can cause the engine to flame out.
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kaddyuk
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 6:53 am

Quoting D5DBY (Thread starter):
.beacuse the compressor in the jet-engine dosent get enough air??

Yup, just like a wing, the blades of the compressor can also stall, creating a back flow of air in the engine which will stall it  Smile

the problem of "compressor stall." This meant that at certain speeds while in flight, the compressor would pull in more air than the rest of the engine could swallow. Compressor stall produced a sudden blast of air that rushed forward within the engine. The engine lost all its thrust, while this air blast sometimes caused severe damage by breaking off compressor blades.

This also happens in reverse when the engine needs more air than the compressor can supply and it starves the engine of air.
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SlamClick
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 7:13 am

There is always some confusion outside the industry over use of the word stall.

We talk about stalls in relation to the wings, or more rarely to flight controls.

Unrelated to that we will talk about compressor stalls.

Both of these things have been thoroughly discussed here in the past and a search ought to turn them up.

Problem is, non-aviation people think of their car "stalling" when they hear these things. Our meanings are quite different from that, and very specific.
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FredT
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 7:16 am

What you need to realize is that compressor/engine stall (or engine surge) is not related to stalling the wing of the aircraft. Wings stall if you exceed a given AoA. Most of the time, this means flying slow. That's not what makes an engine surge.

Engine surges do involve stalling the airfoils of the engine though, as pointed out above.

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air2gxs
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 9:24 am

A jet stalling and flaming out are 2 different things. A stall as described above is basically when the airflow through the compressor is disrupted and the engine surges. Flaming out is when the engine basically runs out of fuel. This does not mean it has run dry, it means the fuel control is no longer supplying fuel to the nozzles, for whatever reason.
 
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HAWK21M
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 12:29 pm

Quoting Air2gxs (Reply 5):
Flaming out is when the engine basically runs out of fuel. This does not mean it has run dry, it means the fuel control is no longer supplying fuel to the nozzles, for whatever reason.

Wouldn't a stoppage of Aiflow for combustion also be termed as Flame out along with Stoppage of Fuel flow to the Fuel nozzles.As Flame out should mean No Ignition of the Fuel-Air mixture occuring by removal of the sources.
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FredT
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 7:21 pm

A flame out can happen with the fuel still flowing. It just means that there is no fire in there. A flame-out could well result from an engine surge.

Rapid power increases (which the engine control systems should make impossible), disturbed airflow into the intakes, high altitude, faulty bleed air valves, worn engines... those are the factors increasing the risk for a surge that I can think of off the top of my head,
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air2gxs
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 8:29 pm

I stand corrected. I was thinking just along the lines of fuel. For some reason (alcohol) my mind seperated airflow from fuel flow.
 
FredT
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RE: Jet-engine, Flame Out?

Fri Sep 02, 2005 9:28 pm

Quoting Air2gxs (Reply 8):
I was thinking just along the lines of fuel.

Having a fuel line inside your head does your thinking little good!  Wink
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D5DBY
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RE: Jet-engine, Flame Out?

Sat Sep 03, 2005 1:15 am

Quoting Kaddyuk (Reply 2):
the problem of "compressor stall." This meant that at certain speeds while in flight, the compressor would pull in more air than the rest of the engine could swallow.

is this true? dosen´t a engine stall/surge acurs when the compressor blades can´t supply the combustion chamber with enough air?

that the compressor is pulling in to much air..that can´t cause a stall/surge can it?

a stall/surge happens because the compressor can´t supply the combustion chamber with enough air...right?
 
FredT
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RE: Jet-engine, Flame Out?

Sat Sep 03, 2005 2:17 am

D5DBY,
nope, the flow through the engine gets choked, compressorblades stall as the airflow slows down, further breakdown of airflow leads to further stalling of compressorblades and possibly even a complete reversal of flow through the compressor. A huge bang is the result. This can even damage the engine if you are unlucky.

Cheers,
Fred
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kaddyuk
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RE: Jet-engine, Flame Out?

Sat Sep 03, 2005 2:38 am

I've tried to find a report but been unlucky...

I CO B742 in the '80s departing from gatwick, suffered a major crosswind which stalled the number one engine completly and affected the number two engine so bad it practically reduced to zero thrust. The aircraft was forced to take off but due to the quick thinking of the flight engineer, it commenced dumping fuel just moments after passing the perimeter fence.

I'd love to read the official report but cant find it...
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VC-10
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RE: Jet-engine, Flame Out?

Sat Sep 03, 2005 2:44 am

Quoting Kaddyuk (Reply 12):
I CO B742 in the '80s departing from gatwick, suffered a major crosswind which stalled the number one engine completly and affected the number two engine so bad it practically reduced to zero thrust. The aircraft was forced to take off but due to the quick thinking of the flight engineer, it commenced dumping fuel just moments after passing the perimeter fence.

I had to boroscope all the engines on that one.
 
D5DBY
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RE: Jet-engine, Flame Out?

Sat Sep 03, 2005 2:59 am

say if u are about to stall the AC for whatever reason...the pilot realizes this and very fast increase the throttle to max(or close to max) to prevent the AC to stall..

is there a risk that because of this fast increase in throttle, and say that this happens at high altitude (30.000 feet) and perhaps also because the AC is flying "slowly"...( due to the AC stall)

in this specific situation, isen´t there a huge risk that the compressor blades can´t keep up the airflow to the engines.....and by that cause one or 2 engines to stall/surge? ( lets say in this example im talking about a MD80)
 
kaddyuk
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RE: Jet-engine, Flame Out?

Sat Sep 03, 2005 2:59 am

Quoting VC-10 (Reply 13):
I had to boroscope all the engines on that one.

Thats freaky  Wink my instructor when studying Module 15 JAR66 (Gas Turbine Engines) used it to highlight the dangers of compressor stall...!
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Jetlagged
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RE: Jet-engine, Flame Out?

Sat Sep 03, 2005 9:26 am

Quoting D5DBY (Reply 14):
say if u are about to stall the AC for whatever reason...the pilot realizes this and very fast increase the throttle to max(or close to max) to prevent the AC to stall..

is there a risk that because of this fast increase in throttle, and say that this happens at high altitude (30.000 feet) and perhaps also because the AC is flying "slowly"...( due to the AC stall)

The engine fuel control unit will limit acceleration (and maybe open bleeds/move stators) to avoid compressor stall.

Quoting D5DBY (Reply 14):
in this specific situation, isen´t there a huge risk that the compressor blades can´t keep up the airflow to the engines.....and by that cause one or 2 engines to stall/surge? ( lets say in this example im talking about a MD80)

With tail mounted engines there is a risk that disturbed airflow from the wings could cause a compressor stall. At the kind of AOA you are at for a wing stall, the wing wake will be well above a typical tail-mounted engine inlet, so no worries there. However you are in much more trouble if the disturbed airflow causes loss of pitch control by affecting the fin mounted horizontal tail (a super-stall).

Why do you think you would be likely to enter a low speed stall condition at 30,000 feet though? Even if this did happen, and both engines flamed out, the pilot could still lower the nose and recover airspeed. From 30,000 feet there would be plenty of time to relight the engines once control was restored.
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HAWK21M
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RE: Jet-engine, Flame Out?

Sat Sep 03, 2005 8:44 pm

Quoting FredT (Reply 11):
A huge bang is the result. This can even damage the engine if you are unlucky

Occurs in R/T mode too.More common.Disapointing to Mx when We hear it.
 Smile

Quoting VC-10 (Reply 13):
I had to boroscope all the engines on that one

Whats the Story behind this Incident.
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MEL
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